JAS 1999 Quarterly Rpt. sidebar
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(Quarterly Report for Jul-Aug-Sep 1999)
GROUNDFISH
ASSESSMENT
Identification
and Characterization of Atka Mackerel Reproductive Habitat
In August 1999, RACE and REFM
fishery scientists collaborated for a second consecutive year to find areas in the
Aleutian Islands where Atka mackerel (Pleurogrammus monopterygius) spawn. No
nesting sites were found the previous summer after searching 10 days in the eastern end of
the Aleutian chain near Unalaska. This years efforts focused in the central
Aleutian Islands region around Seguam Island and near the northeast corner of Amlia
Island.
The basic biology of Atka mackerel
is sparsely studied despite its commercial value and importance as a key forage species
for the endangered Steller sea lion and other marine piscivores. A peculiar aspect
of Atka mackerel life history is that the adults switch from a predominantly pelagic to
mostly demersal existence during the spawning season. In the summer and early fall,
adults migrate to shallower water where females deposit their eggs onto rocky substrate.
Males fertilize the demersal egg clusters and remain behind to guard a territory
containing batches of embryos, nests. Such nesting sites have been
documented in Russian waters but have never been verified in U.S. waters until now.
The commercial fishing vessel Vesteraalen
was chartered and used as the primary support vessel. A 6-m, rigid-hulled inflatable
was deployed from the support vessel and used for exploring nearshore areas.
Underwater video and SCUBA diving were the primary research tools to locate and
study Atka mackerel nesting areas. The towed video camera we used did not have
adequate resolution to detect the embryo clusters as it was dragged through the water.
Direct observations by divers were necessary to verify the presence of nests.
During 5 days of field work, scientists made a total of 18 dives, filmed more
than 8 hours of underwater video footage, collected numerous biological specimens with
hook-and-line (jigging) and spearfishing, and measured depth and temperature at nesting
sites. The principal nesting site chosen for most of this work was on the northeast
side of Seguam Island south of Finch Cove. The depth of the dive site was between 15
and 30 m, and the bottom consisted of rock outcrops interspersed with moderate-sized
boulders less than 0.5 m in diameter. Fist-sized clumps of embryos were
deposited in the interstices of boulders, and their color blended with the encrusting
algae and other marine life. Nest sizes were difficult to discern because males were
guarding nondiscrete batches of embryos spread over areas more than 1 m in diameter.
Behaviors of aggregated adults and guardian males at nesting sites were observed in
situ using an autonomous underwater video recorder. Strip transects were also used
to estimate the density of nests. Stomachs of red Irish lord (Hemilepidotus
jordani), yellow Irish lord (H. hemilepidotus), Pacific cod (Gadus
macrocephalus), and male Atka mackerel that we captured in the nesting area all
contained Atka mackerel embryo masses, indicating predation and cannibalism of Atka
mackerel nests were common.
RACE and REFM scientists plan to
continue exploring the temporal and spatial distribution of Atka mackerel nesting areas in
the central and western Aleutian Islands and learn more about this peculiar fishs
nesting habitat and behavior. Such information may ultimately be useful for
developing an index of population abundance for this important commercial and forage
species.
By Bob Lauth.
The Effect
of Speed on Bottom Tending of a Research Trawl
In late September scientists from
the Groundfish Assessment Program conducted a bottom trawling experiment off the
Washington coast using the chartered commercial fishing trawler Sea Storm in late
September. Trawling operations occurred in depths ranging between 55 and 183
m. The objective of the experiment was to determine the range of trawling speeds
which produces optimal bottom tending performance for our standard Noreastern survey
trawl and to learn how the trawls performance deteriorates at speeds outside this
range.
Specific objectives included:
Monitoring and measuring the
extent of footrope contact with the seafloor at varying vessel speeds ranging from 2.0 to
4.5 knots.
Determining the speed and
direction of ocean bottom currents interacting with the trawl to estimate the speed
of the trawl moving through the water.
Determining the speed at which
footrope contact with the bottom becomes unstable.
Determining if there is a
relationship between speed and footrope height off bottom.
Measuring the time required for
the footrope to settle back to the bottom at varying speeds.
The standard RACE Noreastern
bottom trawl was towed at varying speeds. The codend was left open to avoid capture of any
fish. The trawl speed over the ground and through the water was measured using
differential GPS, a trawl-mounted current meter, and a moored current meter in the
vicinity of our trawling activities. The footrope contact of the trawl was observed at
fishing speeds between 2.0 and 4.5 knots. Bottom contact, including footrope height
off bottom during periods of no contact, was measured using a tilt meter mounted on the
footrope. A self-contained underwater video camera system was used to verify the
tilt meters performance.
Trawling operations first targeted
an area of smooth sand bottom. Paired tows were made in opposing directions to enable us
to measure effects due to prevailing current conditions. A second deeper site
consisting of a level mud substrate was also explored.
By Ken Weinberg.
West Coast
Sediment Map and Relationship to Groundfish Distribution
The Groundfish Assessment Program is
participating in a collaborative, multi-agency effort involving NOAA, the U.S. Geological
Survey (USGS), the Geological Survey of Canada, and the Ocean Sciences Institute (OSI),
University of Sydney, Australia, to make a surficial sediment map of the U.S. west coast
continental shelf and relate the distribution of fish and invertebrate species caught in
RACE triennial bottom trawl surveys to bottom type.
The project uses a fuzzy logic
database, developed by a senior research fellow at OSI, which can use both qualitative as
well as quantitative data. The system enables the user to create numerical values
for qualitative data points or retrieve specific data types based on queries. So far
the scientists have collected and entered about 10,000 data points with good coverage for
large portions of the triennial survey area. They will continue to add more data
sets as they become available and attempt to fill holes in the sediment map. Mark
Zimmermann of the Groundfish Program delivered portions of three seminars describing new
interpretations of RACEBASE data to familiarize USGS with the fisheries data:
Possible importance of rocky
untrawlable areas in biomass estimation of some species
Significance of unusually small
catches in the early years of the survey
The need for a proper species
assemblage analysis for relating fish to habitat type. If the group can demonstrate
relationships between fish and some measure of sediment type, then they may be able to
test the validity of stratum boundaries currently used in the triennial survey, which are
based on latitude and depth, and suggest new boundaries based on other biologically
significant factors.
By Mark Zimmermann.
MIDWATER
ASSESSMENT AND CONSERVATION ENGINEERING
Pollock
Survey of Eastern Bering Sea Shelf
Scientists in the Midwater
Assessment and Conservation Engineering (MACE) Program conducted an acoustic-trawl survey
of walleye pollock on the eastern Bering Sea shelf between 12 June and 29 July aboard the
NOAA ship Miller Freeman. The survey design consisted of north-south transects
spaced 20 nmi apart (except in the horseshoe area where the spacing was 10
nmi) and proceeded from east to west starting at long. 160�W and ending at long.
178�W. Acoustic data were collected continuously along transects between
sunrise and sunset; night operations were devoted mainly to target strength experiments
and net sampling for young-of-the-year pollock and zooplankton. Biological samples
of echosign across the Bering Sea shelf comprised 98 midwater, 14 bottom, 4 Marinovich,
and 48 Methot trawls. We obtained water temperature profiles at each haul location
and other select locations, as well as continuous surface thermosalinograph data.
Preliminary results show pollock acoustic backscatter (from 14 m below the surface
to within 0.5 m of the bottom) absent or very low in the east, but then increasing around
165癢 northwest of Unimak Island (Figure
1, .pdf file). Pollock backscatter was lower between 166�-167癢 and then
increased again, remaining relatively continuous from about 168癢 westward to the
U.S./Russia border. The highest pollock concentrations were between 173癢 and
177癢. In contrast to geographic distributions from previous surveys (1994, 1996,
and 1997), the 1999 pollock distribution was centered farther offshore. Vertical
distribution of echosign was about 50% off bottom (10 m off to the surface) and 50% near
bottom (10 m off to the bottom), except for the horseshoe area and the western-most
transect, where greater than 60% and less than 10% was off bottom, respectively.
West of the Pribilof Islands, pollock were rarely found in waters with bottom depths
shallower than 100 m. Water temperatures were lower than in recent years. Pollock
captured in midwater/bottom trawls ranged from 9-79 cm in length. Adult pollock ($30
cm in length) were found throughout the shelf; smaller fish (<30 cm) were encountered
north of the Pribilof Islands and again west of 172癢 and south of about 61�N.
Pollock smaller than 20 cm (age-1 pollock) were captured only occasionally.
East of the Pribilofs, pollock modal lengths were 36, 47, and 25 cm; west of the
Pribilofs modal lengths were smaller: 30, 45, and 22 cm, respectively. Preliminary
analysis indicates that 8.4% of total pollock acoustic backscatter was located in the
Steller sea lion Critical Habitat (CH) area, 17.5% was east of 170癢 outside of the CH,
and 74.1% was west of 170癢, which was similar to earlier years. Acoustic
backscatter will be scaled with biological data from the trawl catches to provide
estimates of abundance-at-length and age. Preliminary analyses indicate the biomass has
increased from 1998 and the dominant year class is 1996.
By Steve deBlois.
Tests of
Flexible Halibut Excluders for Sole Fisheries
From 21 to 30 August 1999, RACE
scientists tested the effectiveness of devices to exclude halibut from the catches of
commercial sole fisheries. The chartered fishing vessel Golden Fleece, a
110-ft factory trawler, towed a commercial bottom trawl with excluders installed in the
intermediate section, just ahead of the trawls codend. Trawl sites in the Gulf
of Alaska were selected for high abundance of rex, Dover, and flathead soles. The
excluders were based on designs developed by groundfish harvesters, similar to one tested
last year in an experimental fishery sponsored by the Groundfish Forum. These
consisted of a sloped panel with large square holes, crossing the interior of the
intermediate, leading to a flat, horizontal tunnel along the top of the net through which
large halibut can escape. The smaller target species pass through the holes in the
panel and the floor of the tunnel, leading them back to the codend.
The devices tested in August were
flexible enough to be wrapped over a net reel, making them more usable aboard smaller
trawlers (The device tested in 1998 used a rigid panel of welded aluminum.) Other changes
from previous designs included 2 - 3 rods secured across the selection panels to keep them
fully spread and an auxiliary panel that herded fish downward and then forced them against
the selection panel along half of the sloped section and all of the tunnel. Three
selection panels were compared, including mesh panels with 6 X 6-inch and 7 X 7-inch holes
and a flexible grate, constructed of fiberglass rods and hose, with 7 X 7-inch holes.
An auxiliary net and codend were used to recapture fish coming out of the escape
tunnel for comparison with the catch in the main codend.
Preliminary analyses show that the
excluders were quite effective at retaining target species while excluding halibut.
The 6-inch mesh and the 7-inch flexible grate let more than 90% of the halibut that
entered the trawl escape, while retaining approximately 80% of the target species.
The 7-inch mesh excluded only about half of the halibut, but retained more than 95%
of the soles. Further analyses will explore whether the excluders released the
larger soles at a rate different from the rate for the smaller fish.
By Craig Rose.
RECRUITMENT
PROCESSES
Symposium
Marks Polish Centers 25th Year
Members of the Fisheries
Oceanography Coordinated Investigations (FOCI) program traveled to Gdynia and Szczecin,
Poland, during 5-9 July to participate in a symposium marking the 25th anniversary of the
Polish Plankton Sorting Center and to attend the annual meeting of the advisory committee
for the Sorting Center. The Polish Plankton Sorting Center processes approximately
7,000 plankton samples per year that are collected by various NMFS Fisheries Science
Centers. The staff in Poland are highly skilled and experienced in such a demanding
activity and provide NMFS with an important function in a remarkably short
turn-around time.
The symposium in Gdynia entitled
International Symposium on Fisheries Ecosystem Research and Assessments
consisted of 18 presentations, many of which highlighted the contributions of the Sorting
Center to fisheries ecosystem studies. Ann Matarese presented a paper coauthored by
her and Deborah Blood, Advances in the Knowledge of the Distribution and Abundance
Patterns of the Early Life History Stages of Northeast Pacific and Bering Sea Fishes:
Ichthyoplankton Research Conducted by the Alaska Fisheries Science Center
(1971-1996), and a paper by Morgan Busby, herself, Blood, and Ma籫orzata Konieczna
(of the Sorting Center), Advancements in Ichthyoplankton Taxonomy in the
Northeastern Pacific Ocean and Bering Sea: Research Conducted by the Alaska Fisheries
Science Center 1965-1999." Art Kendall presented Status of Recruitment Studies
of Northeast Pacific Fishes and a paper by Jeff Napp and Debbie Siefert entitled
Contributions by Zaklad Sortowania I Oznaczania Planktonu (Morski Instytut Rybacki)
to Fisheries Oceanography in the Northeast Pacific Ocean and Bering Sea.
During the symposium Ken Sherman of the Northeast Fisheries Science Center, Don
Hoss, of the Southeast Fisheries Science Center, and Art Kendall (AFSC) received medals
awarded by President of Poland Aleksander Kwa裯iewski for their contributions to this
cooperative effort between the United States and Poland.
At the advisory committee meeting,
in Szczecin, operations and achievements of the Sorting Center for the previous year were
reviewed, and plans for the coming year were developed. During the meeting, each
staff member of the Sorting Center received certificates from both the Polish government
and NMFS for their outstanding work.
ICES
Symposium
FOCI scientists attended the ICES
Symposium TransAtlantic Study of Calanus, from 24 to 27 August in
Tromso, Norway. They presented one paper (Baier and Napp, Population dynamics
of Calanus marshallae in the southeastern Bering Sea: the influence of
climate) and one poster (Napp and Baier, Calanus marshallae (Frost)
Gonad Maturation and Egg Production in the Southeastern Bering Sea).
Studies in
Russia
Morgan Busby of Recruitment
Processes traveled as an invited visiting scientist to St. Petersburg, Russia, during
10-23 July to conduct research at the Laboratory of Ichthyology of the Zoological
Institute, Russian Academy of Sciences. During his visit he examined type and
nontype specimens of snailfishes (family Liparidae) described from the Sea of Okhotsk and
other localities of the Russian Far East. He also discussed taxonomic problems and
zoogeography of snailfishes in the Bering Sea with ichthyologists of the Zoological
Institute and snailfish expert Dr. David Stein from the United States who was also
visiting the laboratory. In addition, Morgan verified identifications of specimens
of Allocareproctus jordani and Liparis marmoratus collected in the Bering
Sea. These snailfishes were previously known only from the Sea of Okhotsk and Kuril
Island archipelago. He also provided a summary report of some preliminary results of
his research to the Zoological Institute.
By Art Kendall.
Cruises
A member of the Recruitment
Processes Program participated in an ABL Ocean Carrying Capacity cruise to the
southeastern Bering Sea from 12 to 26 July aboard the chartered vessel Great
Pacific.
The purpose of the cruise was to determine the abundance and distribution of young
outmigrating Bristol Bay sockeye salmon. The Recruitment Processes
Programs participation involved the collection of samples to determine
the abundance and distribution of salmon prey and the distribution and abundance of age-0
pollock.
Members of the Recruitment Processes
Program participated in a cruise to the Bering Sea, 20 July-1 August, aboard the Japanese
research vessel Oshoro Maru to monitor the abundance of young-of-the-year walleye
pollock. This was the fifth consecutive year that this survey has been made in
cooperation with Hokkaido University.
Scientists also participated in a
Southeast Bering Sea Carrying Capacity (SEBSCC) cruise during 2 - 19 September in the
southeastern Bering Sea aboard the NOAA ship Miller Freeman. Sampling was conducted
for three separate projects within the SEBSCC program. Principal Investigators included G.
Swartzman from the University of Washington and K. Coyle from the University of Alaska
Fairbanks. The objectives of the cruise were:
To continue studying the effect of
hydrographic fronts on the marine ecology of the Pribilof Islands vicinity.
To continue the acquisition of
long-term monitoring of biological and physical conditions in the southeast Bering Sea.
Scientists from a variety of
institutions participated in the cruise due to the multidisciplinary objectives. Further
details are available in the FOCI Cruise Report.
The hydrographic-front study, which
began in 1994, emphasizes the trophic importance of young-of-the-year (age-0) walleye
pollock in the marine ecology around the Pribilof Islands. As in previous years, CTD
(conductivity-temperature-depth) casts were used to locate the front along two transects
that radiate out from each of the two main islands, St. George and St. Paul. The front is
a region of partially stratified (thermally) water that surrounds each island. Biological
samples, including plankton, micronekton, and nekton samples were collected along each
transect inshore of the front (well mixed), at the front, and offshore (stratified). As in
previous years, almost all fish collected in midwater tows were age-0 pollock, and
jellyfish (Chrysaora melanaster) were a major component of the plankton. Marine
bird observations and multifrequency acoustic data were also collected along each
transect.
The biophysical monitoring of the
southeast Bering Sea involved CTD casts and collecting plankton, and microplankton along
two transects. Transect location was chosen to monitor conditions across the shelf, along
the 70-m isobath, and to coincide with mooring location. Additional sampling was conducted
near each mooring to verify the accuracy of data collected by the moored instruments.
By Art Kendall.
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